Air Traffic Control

Question 1

Principles of radar: Primary vs. Secondary, applications, advantages and disadvantages

Answer 1

Primary Surveillance Radar (PSR):
- Passive detection system
- signal intensity: 1/r^4
- no encoding
- no on boaed equipment needed
- speed detection possible
Example –Precision Approach Radar (PAR)

Secondary Surveillance Radar (SSR)

• Active detection system
• signal intensity 1/r^2
• encoding: Information can be transmitted (altitude, identificationetc.)
• no speed detection
• On-board installation required (transponder)

Question 2

Types of ADS

Answer 2

•ADS-A(addressed)/ADS-C(contracted):
–One-to-one relationship between ground station and aircraft
–Negotiation of required flight parameters
•ADS-B(broadcast):
–Broadcast off light data with out request
–The data can be obtained by any receiver in range

Question 3

ADS-B: Principles and application

Answer 3

Typical flight parameters sent via ADS-B contain:
•ICAO address
•Call sign of the aircraft
•Current altitude
•Selected altitude on mode control panel (MCP)
•Vertical speed
•Ground speed
•True track
•SSR identification code (squawk)
•Ground/air condition

Question 4

Types of ADS( AUTOMATIC DEPENDENCE SURVEILLANCE)

Answer 4

•ADS-A(addressed)/ADS-C(contracted):
–One-to-one relationship between ground station and aircraft
–Negotiation of required flight parameters
•ADS-B(broadcast):
–Broadcast off light data with out request
–The data can be obtained by any receiver in range

Question 5

Voice communication: VHF and HF

Answer 5

• VHF-Band using 117.975 –137.000 MHz
• VHF requires line-of-sight:𝑟𝑚𝑎𝑥=sqrt((𝑅+ℎ)^2−𝑅^2)=sqrt(2𝑅ℎ+ℎ^2)
• Assuming aircraft at 5000 ft(1450 m), max possible range would be 136 km
• HF-Band using 2.8 –22 MHz
• HF communication can reach higher ranges due to reflections in the ionosphere
• HF is therefore used mainly for long flights over water

Question 6

ACARS: Principles and application

Answer 6

Aircraft Communications And Reporting System (ACARS)
•Digital datalink systems to transmit short and simple messages
•Transmission is carried out via ground stations or satellites.
•ACARS was developed by ARINC and put in service in 1978.
•A worldwide ACARS data network has been built by SITA.
•ACARS is designed to meet ARINC 724. 5-71
Events reported by ACARS
•„Out, Off, On, In“ –OOOI:
–Out of the gate
–Off the ground
–On the ground
–Into the gate
•Changes of flight plan (time, routing)
•Delay reports
•Position reports
•Aircraft loading, weight & balance, fuel information
•Weather reports
•Maintenance reports (including engines)•Requests: e.g. gate, catering, clearances
•Passenger information: Connecting flights/gates

POSN47323E012004,ERKIR,185303,340,KOGOL,185652,KPT,M76,26170
Current position: 47.323°N, 12.004°E
Waypoint ERKIR reached at 18:53:03 (UTC) at FL 340
Next waypoint KOGOL will be reached at 18:56:52 (UTC), then to waypoint KPT
Cruising speed: Mach 0.76, Wind 261°with 70 knots